The present invention is generally related to apparatus for treating waste materials and more particularly to apparatus especially suitable for treating urban solid wastes composed chiefly of paper and plastic film.
It is generally known that urban solid wastes are mostly composed of highly heterogeneous materials including a wide variety of different types of items. Accordingly, separation equipment for treating such urban wastes must be capable of coping with the extreme heterogeneity of waste material which is to be involved. Of particular interest from the point of view of the present invention are the problems which arise with regard to treating and separating waste materials which are chiefly composed of paper and plastic films.
A particular problem arising in the treatment of urban wastes occurs during the initial separation stage. At this stage of the separation process, the items included in the waste material must be separated according to their quality and size. Generally, known separation equipment operates on the basis of separating the individual items in the waste material in accordance with weight considerations. That is, lighter items are separated from heavier items within the treatment plants. However, items which operate on the basis of weight differentiation tend to be unsuitable when the urban wastes include a large amount of plastic film which must be separated from paper wastes. This is due to the fact that the specific weights and surface dimensions of these items are approximately the same and it becomes very difficult to distinguish one from the other.
Therefore in the art of urban waste treatment, when urban wastes must be subjected to an initial separation stage, it has heretofore been very difficult to suitably differentiate paper from plastic film and to effect and achieve adequate separation of these materials.
A further consideration in the art of treating waste materials involves the economics of the processes and apparatus utilized. Recovery of waste materials such as plastic films and paper can be of significant commercial value. However, until the present invention, it was not possible to adequately separate these materials with equipment which could be considered suitable from an economic standpoint. It must be understood that if the equipment which must be utilized to treat urban wastes tends to involve complexity or high costs, an economic barrier arises with regard to the practical utilization of such equipment. In the separation of plastic films and paper, it has previously been difficult or impossible to utilize pneumatic or mechanical means to effect the separation process. However, utilization of simple pneumatic or mechanical devices for such a purpose which are capable of operating without high expense can be of significant value in the area of urban waste reclamation.
Accordingly, the present invention is directed toward provision of separation equipment which is especially suitable for separating plastic films and paper in the treatment of urban solid wastes. The invention is directly aimed toward a structural arrangememt whereby such separation of plastic films and paper may occur with adequate effectiveness without introducing problems with regard to the complexities or expense of the apparatus which is utilized.